【紫光同创PGL50H】小眼睛科技盘古50K开发板试用体验之图像灰度显示

在紫光PGL50H上简单实现一下图像灰度化处理。

01 软硬件平台

软件平台：PDS_2022.1
硬件平台：小眼睛科技盘古50K开发板

02 灰度化处理

灰度就是没有色彩, RGB色彩分量全部相等。将像素点RGB值转换为灰度的公式为

Gray = R×0.299 + G×0.587 + B×0.114;

但直接使用FPGA实现浮点运算是不可能的，所以将RGB灰度系数放大1024倍，得到结果后再右移10，即可得到0-255区间大小的灰度值。实现公式为：

Gray = (R×306 + G×601 + B×117)<<10;

03 程序设计

基于小眼睛科技提供的 HDMI 回环实验，对输入的RGB像素值套用灰度公式，然后将行场数据同步信号流水延迟对齐灰度数据输出。

module hdmi_gray_test(
    input wire           sys_clk,     // input system clock 50MHz

    output               rstn_out,
    output               iic_scl,
    inout                iic_sda, 
    output               iic_tx_scl,
    inout                iic_tx_sda, 
    input                pixclk_in,                            
    input                vs_in, 
    input                hs_in, 
    input                de_in,
    input     [7:0]      r_in, 
    input     [7:0]      g_in, 
    input     [7:0]      b_in,  

    output               pixclk_out,                            
    output reg           vs_out, 
    output reg           hs_out, 
    output reg           de_out,
    output reg    [7:0]  r_out, 
    output reg    [7:0]  g_out, 
    output reg    [7:0]  b_out,
    output               led_int
);

reg [15:0]  rstn_1ms       ;
wire        pix_clk        ;
wire        cfg_clk        ;
wire        locked         ;

pll u_pll(
  .clkin1       (sys_clk   ),   // input//50MHz
  .pll_lock     (locked    ),   // output
  .clkout0      (cfg_clk   )    // output//10MHz
);

ms72xx_ctl ms72xx_ctl(
    .clk         (  cfg_clk    ), //input       clk,
    .rst_n       (  rstn_out   ), //input       rstn,
   
    .init_over   (  init_over  ), //output      init_over,
    .iic_tx_scl  (  iic_tx_scl ), //output      iic_scl,
    .iic_tx_sda  (  iic_tx_sda ), //inout       iic_sda
    .iic_scl     (  iic_scl    ), //output      iic_scl,
    .iic_sda     (  iic_sda    )  //inout       iic_sda
);

assign led_int  =  init_over;
assign rstn_out = (rstn_1ms == 16'h2710);
assign pixclk_out = pixclk_in; 

always @(posedge cfg_clk) begin
	if(!locked)                    rstn_1ms <= 16'd0;
	else if(rstn_1ms == 16'h2710)  rstn_1ms <= rstn_1ms;
	else                           rstn_1ms <= rstn_1ms + 1'b1;
end
 
 
reg  [7:0]	gray;
reg  [7:0]	value;
reg       	vs_temp0;
reg       	hs_temp0;
reg       	de_temp0;
reg       	vs_temp1;
reg       	hs_temp1;
reg       	de_temp1;
 
always  @(posedge pixclk_out) begin
	if(!init_over)
		gray <= 8'd0;
	else 
		gray <= (r_in*306 + g_in*601 + b_in*117)>>10; 
end	
 
always  @(posedge pixclk_out) begin
	if(!init_over)
		value <= 8'h00;
	else if(gray >= 8'd150)
		value <= 8'hff;
	else
		value <= 8'h00;
end
 
always  @(posedge pixclk_out) begin
	vs_temp0 <= vs_in	; 
	hs_temp0 <= hs_in   ;
	de_temp0 <= de_in   ;
	vs_temp1 <= vs_temp0;
	hs_temp1 <= hs_temp0;
	de_temp1 <= de_temp0;
end

//HDMI_OUT  =  HDMI_IN 
always  @(posedge pixclk_out) begin
    if(!init_over)begin
	vs_out       <=  1'b0        ;
        hs_out       <=  1'b0        ;
        de_out       <=  1'b0        ;
        r_out        <=  8'b0        ;
        g_out        <=  8'b0        ;
        b_out        <=  8'b0        ;
    end
    else begin
        vs_out       <=  vs_temp0        ;
        hs_out       <=  hs_temp0        ;
        de_out       <=  de_temp0        ;
        r_out        <=  gray         	 ;
        g_out        <=  gray         	 ;
        b_out        <=  gray         	 ;
    end
end

endmodule

04 灰度显示

灰度效果如下视频所示。